US20030123787A1 - Optical cross-connect switch - Google Patents
Optical cross-connect switch Download PDFInfo
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- US20030123787A1 US20030123787A1 US10/318,615 US31861502A US2003123787A1 US 20030123787 A1 US20030123787 A1 US 20030123787A1 US 31861502 A US31861502 A US 31861502A US 2003123787 A1 US2003123787 A1 US 2003123787A1
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- connect switch
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- optical cross
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/35—Optical coupling means having switching means
- G02B6/3502—Optical coupling means having switching means involving direct waveguide displacement, e.g. cantilever type waveguide displacement involving waveguide bending, or displacing an interposed waveguide between stationary waveguides
- G02B6/3504—Rotating, tilting or pivoting the waveguides, or with the waveguides describing a curved path
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/35—Optical coupling means having switching means
- G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
- G02B6/3544—2D constellations, i.e. with switching elements and switched beams located in a plane
- G02B6/3546—NxM switch, i.e. a regular array of switches elements of matrix type constellation
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/35—Optical coupling means having switching means
- G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
- G02B6/356—Switching arrangements, i.e. number of input/output ports and interconnection types in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/35—Optical coupling means having switching means
- G02B6/3564—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details
- G02B6/3568—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details characterised by the actuating force
- G02B6/3578—Piezoelectric force
Definitions
- the present invention relates to an optical cross-connect switch. It specifically relates to an optical cross-connect switch that allows to change the routing of optical signal beams in fiber-optic cable communication systems. More particularly, the invention relates to an integrated optical cross-connect switch comprising a micromechanical steering device on a substrate with a patterned waveguide layer. The invention further relates to an optical cross-connect switch designed to exchange optical signal beams across a switching plane between incoming and outgoing ports.
- optical cross-connect switches or switching fabrics which are controlled by a network management system, are used to adapt the communication system dynamically to high capacity demands that vary in time.
- the entire multiplexed signal of a failed link, connecting a first and second switching station within a network may automatically be switched to a protection fiber.
- the multiplexed signal may also be routed via an optical cross-connect switch of a third switching station in order to increase channel capacity or to reroute traffic of a broken link.
- Optical cross-connect switches which are described for example in U.S. Pat. No. 6,002,818, are therefore used to provide switchable cross-connects between optical fibers.
- One such cross-connect switch comprises piezoelectric lateral actuators for the optical fibers. The switching is accomplished therein by using a piezoelectric actuator which laterally translates the input fiber relative to the axis of a first collimation lens, thereby enabling the optical beam to be steered to a second collimation lens where another piezoelectric actuator has translated the end of an outgoing fiber into the location where it receives the optical beam.
- steering units are required at the input fibers and output fibers. Besides being costly, the physical size of these beam-steering units affects the overall size of the optical crossbar.
- Another cross-connect switch comprises a beam-steering unit with rotating prisms to provide beam deflection from a transmitter side to a receiver side.
- Optical communication initially was proposed to be based on the idea of switching optical signals from a selectable one of a plurality of incoming fibers to a selectable one of a plurality of outgoing fibers by orienting the end of the selected incoming fiber relative to a lens thereby providing a radiation beam of variable direction.
- An example therefore is disclosed in U.S. Pat. No. 4,512,036.
- the free end of an optical fiber is moved by a piezoelectric bender element. That free end provides a beam of electromagnetic radiation which either impinges on a freestanding lens or on a lens that is mounted at the free end of the bender element.
- Optical steering units comprising rotating prisms or further optical elements are hence known which direct an optical signal, emanating from an incoming optical fiber, towards an outgoing optical fiber. Switching of the optical signals in such devices is therefore performed in free-space.
- An optical cross-connect switch designed to switch optical beams in free-space is described in WO 00/79311.
- This optical switch comprises, mounted on a base, at least one controllable actuator for positioning an optical element to guide an optical signal on a selected free-space switching path, within an optical path plane parallel to the base, from an input optical fiber to an output optical fiber.
- the optical beam can be directed in free-space by means of diffractive, refractive or reflective optical elements.
- MEMS microelectromechanical systems
- Micromechanical structures are the basis of microactuators that are developed for the application in several technical fields, particularly for optical systems. Microactuators operating based on thermal effects are described in J. Micromech. Microeng., 10 (2000) 260-264. Electrostatic microactuators are described in WO 99/37013. Piezoelectric microactuators are described in U.S. Pat. No. 4,512,036. Microactuators operating based on the generation of surface acoustic waves are described in JP 10-327590.
- a further cross-connect switch using reflective optical elements for redirecting an optical beam is described in U.S. Pat. No. 6,144,781.
- a reflective optical element is disposed at the intersection of a first and a second light beam emanating from a corresponding first and second input in such a way that the light beams are directed to a first or a second output respectively.
- the invention is related to an optical cross-connect switch comprising a waveguide connected with one waveguide end to a first optical port and connected with its other waveguide end to a steering device for directing an optical signal beam from said first optical port to a second optical port, said waveguide comprising a patterned waveguide layer disposed on a substrate.
- This arrangement has the advantage that it is as a whole manufacturable by a lithographic process. It does not need a separate fiber to be combined, and hence aligned, with the steering part of the switch.
- the substrate and the waveguide can be patterned in one common process. This simplifies the manufacturing. It further avoids the necessity of alignment.
- the ports indicate locations where the optical signal beams enter the optical cross-connect switch and not a special embodiment of the entry points or the means by which the optical signal beams enter the optical cross-connect switch.
- a port may therefore be a unit in which optical waveguides are coupled or a location where optical signal beams are entering the optical cross-connect switch e.g. by means of a waveguide which is coupled to an external device.
- the location of the port could be defined as the output port of the external device.
- the steering device can be arranged in a cavity in the substrate.
- the optical cross-connect switch then comprises a substrate, which is partially covered by a waveguide layer and a cladding layer, patterned for example by etching processes, with at least one waveguide, connected with one end to one of the optical ports and with the other end, comprising core and cladding, unsupported by the substrate or remaining layers and extending into a switching plane above the cavity, which is located in the substrate.
- the steering device In the cavity the steering device is arranged, designed to direct the free waveguide end in a selectable direction within the switching plane towards an optical element, such as a free end of a further waveguide, designed to receive or send optical signal beams.
- the optical cross-connect switch can be used to construct large switching fabrics with numerous peripheral optical ports or small switching units within an optoelectronic comprising for example only three or two internal optical ports that are connected for example to communication modules of the optoelectronic integrated circuit.
- the optical cross-connect switch preferably comprises a slab waveguide module positioned within the switching plane in order to transfer the optical signal beams between a waveguide connected to the first set of optical ports and a waveguide of the second set of optical ports.
- the slab waveguide module provides for a guiding of the optical signal beam that is laterally less constraint than vertically.
- the steering device preferably comprises a head element, which is pivotally supported by an anchor and which holds a corresponding free waveguide end in such a way that the head element can be rotated by means of an actuator thus directing the free waveguide end in a selectable direction within the switching plane.
- the head element is preferably connected to the actuator and to the anchor by means of elastic beams which support rotation of the head element around an axis that is aligned substantially perpendicular to the switching plane thus keeping the free waveguide end in every direction angle stabilized within the switching plane.
- the head element is connected to the actuator by means of the free waveguide end which is elastically suspended on the front end of the actuator. This embodiment allows the fabrication of the head element and the actuator independently from each other.
- the actuator is designed to rotate the head element with forces generated by means of a piezoelectric, electrostatic, acoustic or thermal effect.
- the actuator is a thermally controlled cantilever arranged approximately in parallel to a free waveguide end.
- the actuator has one or two arms, each comprising several actuating beams arranged substantially in parallel, connected to each other at their ends and arranged adjacent to heater elements for individually heating and thus asymmetrically expanding the actuating beams in order to generate a lateral movement at the front end of the actuator and consequently a rotation of the connected head element relative to the supporting anchor.
- the solution allows to fabricate the elements of the steering device including the interconnecting beams in one piece respectively from the same substrate by use of micromachining technology.
- Cross-connect switches can therefore be fabricated at reduced cost with high packing density.
- FIG. 1 shows a sectional view of an optical cross-connect switch with a first and a second set of waveguides arranged with their free waveguide ends aligned by means of waveguide steering devices on opposite sides of a slab waveguide module;
- FIG. 2 a shows a more detailed view of two of the waveguide steering devices of the optical cross-connect switch shown in FIG. 1;
- FIG. 2 b shows a side elevation of a cut along line A-A in FIG. 2 a;
- FIG. 3 shows a more detailed view of a head element of a waveguide steering device
- FIG. 4 a shows a three-dimensional view of a part of an optical cross-connect switch embedded in a layered optoelectronic integrated circuit with a free waveguide end pointing into a first direction;
- FIG. 4 b shows a three-dimensional view of the part of an optical cross-connect switch embedded in a layered optoelectronic integrated circuit with the free waveguide end pointing into a second direction;
- FIG. 5 shows a second embodiment with two waveguide steering devices
- FIG. 6 shows a third embodiment with two waveguide steering devices.
- FIG. 1 shows a sectional view of an optical cross-connect switch 1 comprising a substrate 8 bearing a frame 82 and a first set of waveguides 201 , 202 , 203 , 204 , 205 , 206 .
- the substrate 8 has a sheetlike form, i.e. is essentially planar, which means that it has a substrate plane whose extension in both plane dimensions is larger than the substrate thickness.
- the switch 1 further comprises a first set of optical ports 101 , 102 , 103 , 104 , 105 , 106 at a first end 1 a of the substrate 8 .
- Each of the waveguides 201 , 202 , 203 , 204 , 205 , 206 is connected with a first waveguide end 21 to one of the optical ports 101 , 102 , 103 , 104 , 105 , 106 .
- the frame 82 comprises a waveguide layer 84 exhibiting a preferential mode-propagation direction in a plane parallel to or identical with the substrate plane.
- the frame 82 further comprises on the waveguide layer 84 on its side opposite the substrate 8 , a cladding layer 83 .
- the frame 82 is here unified with the first waveguide ends 21 . More precisely the first waveguide ends 21 and the frame 82 are of unitary construction. Hence the first waveguide ends 21 are also disposed on the substrate 8 , which makes the first waveguide ends 21 to fixed waveguide ends 21 .
- the waveguide layer 84 and the cladding layer 83 are patterned to form the fixed waveguide ends 21 .
- the waveguide layer 84 is patterned to comprise for each of the waveguides 201 - 206 a ridge that forms a respective waveguide core.
- the cladding layer 83 is automatically patterned by depositing it on the patterned waveguide layer 84 thereby forming over each waveguide core ridge a cladding ridge with inclined sidewalls.
- the fixed waveguide ends 21 here comprise a patterned part of the waveguide layer 84 and cladding layer 83 .
- the opposite waveguide ends 22 of the waveguides 201 - 206 extend partially across a first cavity 81 a in the substrate 8 . Since these opposite waveguide ends 22 are standing unsupported and free with respect to the substrate 8 they are also referred to as free waveguide ends 22 .
- the free waveguide ends 22 and the fixed waveguide ends 21 are of unitary construction. This can be achieved by manufacturing them from a common source structure, preferably in a common process step.
- the source structure can be the waveguide layer 84 with the waveguide core ridge and the cladding layer 83 with the cladding ridge.
- the remaining structure comprising the waveguide core with the corresponding cladding, represent the waveguides 201 - 206 comprising the patterned waveguide layer 84 and cladding layer 83 , lying with their fixed waveguide ends 21 on the substrate 8 .
- a manufacturing process step sequence for manufacturing the above described structure would hence be to provide the substrate 8 , deposit thereon the patterned waveguide layer 84 , deposit thereon the cladding layer 83 , remove these two layers in the area around the free waveguide ends 22 and above the first cavity 81 , then creating the first cavity 81 by removing the substrate 8 in that area.
- a steering device 10 is arranged for directing the respective free waveguide end 22 in a selectable direction within a switching plane, that is preferably identical with or parallel to the plane of the substrate 8 .
- Each of the waveguides 211 , 212 , 213 , 214 , 215 , 216 is connected with a first waveguide end 21 to one of the optical ports 111 , 112 , 113 , 114 , 115 , 116 .
- the opposite waveguide ends 22 of the waveguides 211 - 216 extend partially across a second cavity 81 b above the substrate 8 within the frame 82 .
- a steering device 10 is disposed for directing the respective free waveguide end 22 in a selectable direction within the switching plane.
- the arrangement of the switch 1 is here symmetric along the line separating the one end 1 a and the opposite end 1 b of the switch 1 .
- an optical signal beam 4 guided in that waveguide can be directed towards an optical element designed to receive that optical signal beam 4 , such as here the free end 22 of one waveguide of the second set of waveguides 211 - 216 at the opposite end 1 b of the optical cross-connect switch 1 .
- the steering device 10 comprises an actuator 5 and a head element 6 .
- the end of the free waveguide end 22 that is remote from the substrate 8 and extending partially across the first cavity 81 a is hereinafter referred to as remote waveguide end.
- the actuator 5 is here a longitudinal element that is disposed along some part of the length of the free waveguide end 22 and is designed to be able to provide for a lateral force on the free waveguide end 22 with respect to the fixed waveguide end 21 . More precisely the actuator 5 extends from the substrate 8 into the first cavity 81 a along some part of the length of the free waveguide end 22 .
- the head element 6 is arranged at the remote waveguide end and is rotatable for changing the direction of the corresponding free waveguide end 22 , i.e. the direction of the optical signal beam 4 emanating from the remote waveguide end.
- the free waveguide end 22 respectively the remote waveguide end thereof, is preferably preshaped such that it is compliant to flexure and/or torque applied by the steering device 10 , and prevented from retraction in case that the direction is changed. Such a shape would for example be an S-shape.
- the actuator 5 For changing the beam direction at the free waveguide end 22 , the actuator 5 provides for a lateral force and hence a lateral shift of the remote waveguide end of the free waveguide end 22 . That lateral shift is translated by means of the head element 6 into a swiveling of the remote waveguide end, which has the effect of a corresponding swiveling of the beam direction.
- the optical cross-connect switch 1 further comprises a slab waveguide module 3 that is arranged between the first cavity 81 a and the second cavity 81 b.
- the slab waveguide module 3 is designed to guide the one or more optical signal beams 4 between the free waveguide ends 22 of the waveguides of the first set of waveguides 201 - 206 and the waveguides of the second set of waveguides 211 - 216 . Between the slab waveguide module 3 and each of the free waveguide ends 22 a gap 32 exists.
- the slab waveguide module 3 preferably also comprises a part of the waveguide layer 84 and the cladding layer 83 on the substrate 8 , and can therefore easily be fabricated by removing a corresponding section from the waveguide layer 84 and the cladding layer 83 .
- the slab waveguide module 3 and the waveguides 201 - 206 lie in a common plane which plane is identical or parallel to the switching plane.
- the waveguides 201 - 206 and the slab waveguide module 3 are fabricatable in a single patterning process. Such patterning process can be e.g.
- the manufacturing sequence described above automatically creates the slab waveguide module 3 by leaving the substrate 8 with the waveguide layer 84 and the cladding layer 83 in the area outside of the cavities 81 a , 81 b.
- the steering device 10 is located between the waveguide layer 84 and the substrate 8 .
- the structure and functionality of the optical cross-connect switch 1 is preferably symmetric.
- the corresponding opposite free waveguide ends 22 are aligned towards each other by means of the corresponding steering devices 10 , which here are identical in their design to the steering devices 10 for the first set of waveguides 201 - 206 .
- One such optical signal beam 4 can be transmitted between the free waveguide end 22 of one waveguide of the first set of waveguides 201 - 206 and the free waveguide end 22 of one waveguide of the second set of waveguides 211 - 216 through free-space and/or through the slab waveguide module 3 .
- the slab waveguide module 3 comprises adjacent to each remote waveguide end an adaptation section 31 which is curved in such a way that the gap 32 between the slab waveguide module 3 and the respective free waveguide end 22 is substantially constant for several selectable directions.
- the optical cross-connect switch 1 hence allows the selectable transfer of the optical signal beams 4 between the free waveguide ends 22 of the first set of waveguides 201 - 206 and the free waveguide ends 22 of the second set of waveguides 211 - 216 through the slab waveguide module 3 that acts as a coupler element.
- the directional steering of the free waveguide end 22 can be performed with a micro-electromechanical-system, which here is the steering device 10 .
- the steering device 10 comprises the head element 6 designed to hold and rotate the corresponding remote waveguide end relative to an axis aligned substantially perpendicular to the switching plane.
- a rotation of the head element 6 in order to establish a selected signal beam path within the switching plane is performed by an electromechanical actuator, which here is the actuator 5 .
- the frame 82 can serve for coupling the waveguides 201 - 206 to the optical ports 101 - 106 which can be optical fiber ends. Therefore the frame 82 can e.g. be structured to have grooves, e.g. V-grooves for receiving and aligning the optical ports 101 - 106 . This function can also be achieved by other means. Hence the frame 82 is not essential for the functionality of the switch 1 .
- FIG. 2 a shows two of the waveguide steering devices 10 of the optical cross-connect switch 1 of FIG. 1.
- FIG. 2 b shows a cut view along the line A-A in FIG. 2 a.
- One of the steering devices 10 holds the free waveguide end 22 of a first waveguide 201 and one of the steering devices 10 , here referred to as the second steering device 10 , holds the free waveguide end 22 of a second waveguide 202 .
- Each of the steering devices 10 comprises the head element 6 , which is pivotally supported by an anchor 61 and which holds the free waveguide end 22 at its end remote from the frame 82 . It further comprises the elongated actuator 5 having two ends, one fixed end and one free end. The actuator 5 is thermally driven. It is arranged substantially parallel to the corresponding free waveguide end 22 and is equipped with two arms 51 , each comprising two parallel actuation beams 52 in line with lever elements 53 that are connected to each other at their ends by means of a yoke 58 which holds a yoke beam 59 .
- the actuation beams 52 which at the fixed end of the actuator 5 emanate from the substrate 8 , carry electrically resistive heaters 54 , 55 for individually heating and thus asymmetrically expanding the actuation beams 52 in order to generate a lateral movement at the free end of the actuator 5 and consequently a rotation of the connected head element 6 relative to the anchor 61 .
- electrically resistive heaters 54 , 55 for individually heating and thus asymmetrically expanding the actuation beams 52 in order to generate a lateral movement at the free end of the actuator 5 and consequently a rotation of the connected head element 6 relative to the anchor 61 .
- the heater 54 for effecting the asymmetrical expansion of the actuation beams 52 , also only one of the actuation beams 52 can be equipped with the heater 54 .
- the lateral movement of the free end of the actuator 5 hence causes a rotational movement of the head element 6 , turning the remote waveguide end of the attached free waveguide end 22 into a desired direction.
- the remote waveguide end of the first waveguide 201 is at least laterally fixed at the head element 6 by means of spacers 63 , wherein “lateral” is meant in a direction within the switching plane, substantially perpendicular to the beam direction.
- a terminating mode converter 23 is arranged, for collimating the outgoing beam of the respective optical signal beam 4 in horizontal and/or vertical direction.
- the terminating mode converter 23 has here a convex end surface that has substantially the same radius as the corresponding opposite surface of the slab waveguide module 3 .
- the mode converter 23 is designed to create an expanded beam within the gap 32 between the free waveguide end 22 and the slab waveguide module 3 thus optimizing the coupling efficiency therebetween but also preventing beam divergence in the slab waveguide region.
- the mode converter 23 which could comprise a gradually enlarged element of the free waveguide end 22 acts as a collimating element focusing the emitted beam.
- the head element 6 is shaped in a similar form at its end that is closer to the slab waveguide module 3 .
- a small lateral movement of the actuator 5 results in a relatively large deflection of the free waveguide end 22 being translated into a corresponding big angle change of the corresponding beam direction.
- Such a steering device 10 and hence the whole optical cross-connect switch 1 can hence be realized in small dimensions, nevertheless allowing a relatively broad selection of possible beam directions.
- FIG. 2 a The actuation of the first steering device 10 holding the first waveguide 201 is depicted in FIG. 2 a in an off-state.
- the actuation of the second waveguide steering device 10 holding the second waveguide 202 is in contrast depicted in an on-state, resulting in the guidance of the corresponding optical beam 4 through the corresponding turned remote waveguide end at an angle Q towards a receiving waveguide, e.g. the waveguide 214 as shown in FIG. 1.
- the actuation of the steering device 10 holding the second waveguide 202 is effected by heating and thereby thermally expanding the beams 54 on one side of each arm 51 more than the beams 55 on the other side of each arm 51 .
- Heating and thermally expanding the other beams 55 more than the corresponding beams 54 would result in a lateral movement of the front end of the arms 51 in the opposite direction.
- the thermally driven actuators 5 can be used for creating large displacements of the yokes 85 and hence the remote waveguide ends with high forces. They can be based on the thermal expansion of two different materials (bimaterial actuators) or of two coupled beams of an actuator arm at different temperatures. The disadvantage of coupled linear and angular movement is overcome by coupling two of these arms.
- the actuator 5 is at its fixed end supported by the substrate 8 .
- the anchor 61 is realized as a protrusion on the substrate 8 .
- the free waveguide end 22 hence runs along substantially the same direction as the actuator 5 , above the same with respect to the substrate 8 and is held at its remote waveguide end by the head element 6 .
- the process for manufacturing the switch 1 including the steering devices 10 would include a step of manufacturing the steering device 10 by structuring the substrate 8 in the cavity 81 a , 81 b to thereafter have the steering device 10 .
- the steering device 10 and the substrate 8 would be of uniform construction. This would not include the heaters 54 , 55 since these would be made of a different material, as stated above.
- the heaters 54 , 55 would hence be arranged after having created the underlying structure of the steering device 10 that comprises the substrate material.
- the structuring of the substrate 8 to form the steering device 10 without the heaters 54 , 55 can be done by lithographic process steps. It is also possible to produce the steering device 10 separately and then assemble it into the cavity 81 , 81 b in the substrate 8 . Also a combination of such assembly with parts of the steering device 10 having been manufactured directly within the cavity 81 , 81 b from the substrate 8 , e.g. the anchor 61 , can be made.
- FIG. 3 shows a more detailed view of the anchored head element 6 of the second waveguide steering device 10 shown in FIG. 2 a.
- the waveguide steering device 10 comprises the head element 6 which by means of elastic primary beams 64 and secondary beams 65 is connected to the anchor 61 .
- the anchor 61 which may comprise one or more elements, acts as a pivot-bearing allowing the head element 6 to rotate around the point where the primary beams 64 are connected to the anchor 61 .
- the steering device 10 further comprises the actuator 5 with a front end comprising the elastic yoke beam 59 , which by means of the further beam or rod 62 is connected to the head element 6 .
- the elastic yoke beam 59 is attached to the yoke 58 and provides for a fixation of the head element 6 to the actuator 5 that keeps the remote waveguide end of the free waveguide end 22 tiltable with respect to its longitudinal extension.
- the elements of the steering device 10 can be at least partially fabricated in one piece on the substrate 8 being a bulk substrate, by means of micro-fabrication.
- the optical cross-connect switch 1 can therefore be realized for example in an optoelectronic integrated circuit without insertion of externally manufactured optical elements such as mirrors or lenses.
- FIG. 4 a shows a three-dimensional view of a section of an optoelectronic integrated circuit comprising the switch 1 as described.
- the substrate 8 comprises the first cavity 81 a with the steering device 10 integrated therein which holds the free waveguide end 22 of the waveguide 201 fastened to its head element 6 .
- the head element 6 which is rotatably mounted by means of the anchor 61 (not shown), is connected to the yoke beam 59 of the thermally driven actuator 5 which extends out of a section of the substrate 8 , which section forms a sidewall of the first cavity 81 a.
- each cantilever arm 51 On the two actuating beams 52 of each cantilever arm 51 the electrically resistive elements 54 , 55 are arranged, usable for individually heating and thus asymmetrically expanding the actuating beams 52 in order to generate a lateral movement at the front end of the actuator 5 and consequently a rotation of the connected head element 6 relative to the anchor 61 .
- FIG. 4 b the same arrangement as in FIG. 4 a is depicted, but here the free waveguide end 22 is deflected to change its output direction.
- the two actuating beams 52 of each cantilever arm 51 are asymmetrically expanded, thereby generating a lateral movement at the front end of the actuator 5 and consequently a rotation of the connected head element 6 relative to the anchor 61 .
- a force F generated by the actuator 5 is applied to the pivotally supported head element 6 , which transforms this force F into a corresponding rotational moment M to the remote waveguide end of the free waveguide end 22 of the first waveguide 201 .
- the slab waveguide module 3 is an element that can be fabricated from the waveguide layer 84 , the cladding layer 83 and the substrate 8 .
- This slab waveguide module 3 has the functionality of a planar waveguide layer, i.e. has extensions in a plane parallel to or identical with the substrate plane or the switching plane, which here is the plane in which the various selectable directions of the optical signal beams 4 lie, which extensions are bigger than the thickness of the slab waveguide module 3 .
- the slab waveguide module 3 thereby allows a transfer of the optical signal beam 4 that is laterally, i.e. in the switching plane, less constraint than in the planes perpendicular thereto.
- the free waveguide end 22 could also be aligned with a further optical receiver such as another waveguide end which might be firmly aligned.
- the slab waveguide module 3 could be patterned accordingly.
- the optical cross-connect switch 1 could therefore be realized with the steering device 10 holding the free waveguide end 22 of the first waveguide 201 and e.g. two angularly offset fixed waveguide ends 22 located in opposition thereof.
- FIG. 5 shows a second embodiment of the waveguide steering device 10 .
- the waveguide steering device 10 pertaining to the first waveguide 201 is depicted in an off-state and comprises the actuator 5 with a single arm 51 which over an elastic beam 62 is connected to the head element 6 which is further connected to the anchor 61 acting as pivot bearing.
- the arm 51 comprises two actuation beams 52 with one heater 54 , 55 on each of these actuation beams 52 .
- the anchor 61 is arranged sideways to the arm 51 when viewed perpendicular to the switching plane, i.e. in direction of the axis of the anchor 61 .
- the waveguide steering device 10 pertaining to the second waveguide 202 is depicted in an on-state, i.e. by deflection of the actuator 5 the head element 6 is turned around the fixing point provided by the anchor 61 .
- the waveguide steering device 10 shown in FIG. 6 comprises the first waveguide 201 with the dual-arm cantilever actuator 5 and the head element 6 , which are connected to one another by means of the attached waveguide end 22 of the corresponding first waveguide 201 .
- Each arm 51 comprises the two actuation beams 52 with one heater 54 , 55 on each of these actuation beams 52 .
- the head element 6 is connected via the primary and secondary beams 64 , 65 to elements of the anchor 61 acting as pivot bearing.
- the anchor 61 comprises here two anchor elements, one of them respectively being arranged to either side of the remote waveguide end and being fixed at the substrate 8 and being connected to each other via the primary and secondary beams 64 , 65 .
- the front ends of the actuator arms 51 are connected to a bearing element 56 by means of the yoke beams 59 .
- the bearing element 56 and the head element 6 which are mechanically connected by means of the free waveguide end 22 are mutually aligned and rotated correspondingly whenever a lateral movement of the actuator arms 51 occurs, thus directing the free waveguide end 22 in a selected direction.
- the waveguide steering device 10 pertaining to the first waveguide 201 is depicted in an off-state.
- the waveguide steering device 10 pertaining to the second waveguide 202 is depicted in an on-state, i.e. by deflection of the actuator 5 the head element 6 is turned around the fixing point provided by the anchor 61 .
- the solution can also be applied in cross-connect systems comprising protection fibers that are assigned to a single fiber for protection purposes only.
- a protection fiber could therefore be aligned firmly towards an opposite waveguide end 22 which in case of a failure of the standard connection would be redirected towards the end 22 of the protection fiber.
- a lower cladding layer can be arranged under the waveguide layer.
- Such lower cladding layer can e.g. comprise an oxide layer such as SiO 2 on a silicon substrate 8 .
- This lower cladding layer then provides for a more symmetrical mode form, facilitating coupling to other waveguides. All patterning steps that affect the waveguide layer 84 can be performed on the cladding layer 83 and the lower cladding layer as well, such that the final pattern is identical through all three layers.
- the complete steering device 10 can be manufactured from the substrate 8 , using microfabrication, nanostructuring or lithographic process steps. For such process steps it is of advantage if the layout of the steering device 10 is designed such that in a view perpendicular to the substrate plane, at least the arm or arms 51 are positioned lateral to the free waveguide end 22 . Thereby, the arms 51 can be manufactured by exposing the substrate 8 to processing means, such as optical, liquid or gaseous means, directed substantially perpendicularly to the substrate plane.
- processing means such as optical, liquid or gaseous means
- All parts of the steering device 10 that lie underneath the free waveguide end 22 can be manufactured by applying process steps in which the processing agents can reach the structure to be manufactured also underneath the free waveguide end 22 .
- a possibility is also to apply process steps that reach the target location from underneath the substrate 8 .
- Therefor openings that reach the cavity 81 a , 81 b from the underside of the substrate 8 , i.e. from the side opposite the cavity 81 , 81 b , can be manufactured and used.
Abstract
The invention is related to an optical cross-connect switch comprising a waveguide connected with one waveguide end to a first optical port and connected with its other waveguide end to a steering device for directing an optical signal beam from said first optical port to a second optical port, said waveguide comprising a patterned waveguide layer disposed on a substrate. The steering device can be arranged in a cavity in the substrate. The optical cross-connect switch then comprises a substrate, which is partially covered by a waveguide layer and a cladding layer, patterned for example by etching processes, with at least one waveguide, connected with one end to one of the optical ports and with the other end, comprising core and cladding, unsupported by the substrate or remaining layers and extending into a switching plane above the cavity, which is located in the substrate. In the cavity the steering device is arranged, designed to direct the free waveguide end in a selectable direction within the switching plane towards an optical element, such as a free end of a further waveguide, designed to receive or send optical signal beams. The optical cross-connect switch preferably comprises a slab waveguide module positioned within the switching plane in order to transfer the optical signal beams between a waveguide connected to the first set of optical ports and a waveguide of the second set of optical ports.
Description
- The present invention relates to an optical cross-connect switch. It specifically relates to an optical cross-connect switch that allows to change the routing of optical signal beams in fiber-optic cable communication systems. More particularly, the invention relates to an integrated optical cross-connect switch comprising a micromechanical steering device on a substrate with a patterned waveguide layer. The invention further relates to an optical cross-connect switch designed to exchange optical signal beams across a switching plane between incoming and outgoing ports.
- According to Jerry D. Gibson, THE COMMUNICATIONS HANDBOOK, CRC PRESS, Boca Raton 1997, chapter 37, pages 513-528 the migration of photonics into switching is occurring in a variety of ways. This is happening because of the large variety of switching tasks to be performed in a modern communication network. The different switching tasks range from ensuring that major trunks have the ability to be switched from one route to another when a catastrophic accident destroys a route, to the real-time switching on a per call basis. A fiber optic communication network is operating at data rates from a few megabit per second up to 2.5 Gb/s and beyond. At the 2.5 Gb/s rate, several thousand digitized voice channels, each operating at 64 kb/s, can be transmitted along a single fiber using time-division multiplexing. In reconfigurable optical networks, optical cross-connect switches or switching fabrics, which are controlled by a network management system, are used to adapt the communication system dynamically to high capacity demands that vary in time.
- In the event of a failure the entire multiplexed signal of a failed link, connecting a first and second switching station within a network, may automatically be switched to a protection fiber. The multiplexed signal may also be routed via an optical cross-connect switch of a third switching station in order to increase channel capacity or to reroute traffic of a broken link.
- Optical cross-connect switches, which are described for example in U.S. Pat. No. 6,002,818, are therefore used to provide switchable cross-connects between optical fibers. One such cross-connect switch comprises piezoelectric lateral actuators for the optical fibers. The switching is accomplished therein by using a piezoelectric actuator which laterally translates the input fiber relative to the axis of a first collimation lens, thereby enabling the optical beam to be steered to a second collimation lens where another piezoelectric actuator has translated the end of an outgoing fiber into the location where it receives the optical beam. In this technique of steering optical fibers, steering units are required at the input fibers and output fibers. Besides being costly, the physical size of these beam-steering units affects the overall size of the optical crossbar. Another cross-connect switch comprises a beam-steering unit with rotating prisms to provide beam deflection from a transmitter side to a receiver side.
- Optical communication initially was proposed to be based on the idea of switching optical signals from a selectable one of a plurality of incoming fibers to a selectable one of a plurality of outgoing fibers by orienting the end of the selected incoming fiber relative to a lens thereby providing a radiation beam of variable direction. An example therefore is disclosed in U.S. Pat. No. 4,512,036. Therein the free end of an optical fiber is moved by a piezoelectric bender element. That free end provides a beam of electromagnetic radiation which either impinges on a freestanding lens or on a lens that is mounted at the free end of the bender element.
- Optical steering units comprising rotating prisms or further optical elements are hence known which direct an optical signal, emanating from an incoming optical fiber, towards an outgoing optical fiber. Switching of the optical signals in such devices is therefore performed in free-space.
- An optical cross-connect switch designed to switch optical beams in free-space is described in WO 00/79311. This optical switch comprises, mounted on a base, at least one controllable actuator for positioning an optical element to guide an optical signal on a selected free-space switching path, within an optical path plane parallel to the base, from an input optical fiber to an output optical fiber. The optical beam can be directed in free-space by means of diffractive, refractive or reflective optical elements. By using microelectromechanical systems (MEMS) for actuating the optical elements the optical cross-connect switch can be made in reduced size.
- Micromechanical structures are the basis of microactuators that are developed for the application in several technical fields, particularly for optical systems. Microactuators operating based on thermal effects are described in J. Micromech. Microeng., 10 (2000) 260-264. Electrostatic microactuators are described in WO 99/37013. Piezoelectric microactuators are described in U.S. Pat. No. 4,512,036. Microactuators operating based on the generation of surface acoustic waves are described in JP 10-327590.
- A further cross-connect switch using reflective optical elements for redirecting an optical beam is described in U.S. Pat. No. 6,144,781. In this system a reflective optical element is disposed at the intersection of a first and a second light beam emanating from a corresponding first and second input in such a way that the light beams are directed to a first or a second output respectively.
- When placing diffractive, refractive or reflective optical elements in free-space within an optical cross-connect switch in order to redirect an optical beam, several aspects require consideration.
- First of all the production, mounting and alignment of the optical elements involve considerable costs. Production of optoelectronic integrated circuits (OEICs) incorporating the optical elements creates further problems since the relatively large size of optical elements further requires a corresponding size of the free-space switching region resulting in a comparably large dimension of the optical cross-connect switch. Transferring an optical beam through several optical elements may in addition cause transmission losses.
- It would therefore be desirable to improve the described optical cross-connect switches.
- It would be desirable in particular to provide an optical cross-connect switch that can be produced at reduced cost.
- More particularly it would be desirable to create an optical cross-connect switch that can be realized as an optoelectronic integrated circuit, using a process of comparably low complexity.
- It would further be desirable to create an optical cross-connect switch incorporating a reduced number of externally produced optical elements in order to further reduce costs and to avoid transmission losses.
- It would be desirable in particular to provide an optical cross-connect switch of smaller size thereby allowing the connection of an increased number of optical fibers for switching purposes.
- The above and other objects of the present invention are achieved by an optical cross-connect switch according to
claim 1. - The invention is related to an optical cross-connect switch comprising a waveguide connected with one waveguide end to a first optical port and connected with its other waveguide end to a steering device for directing an optical signal beam from said first optical port to a second optical port, said waveguide comprising a patterned waveguide layer disposed on a substrate.
- This arrangement has the advantage that it is as a whole manufacturable by a lithographic process. It does not need a separate fiber to be combined, and hence aligned, with the steering part of the switch. Here the substrate and the waveguide can be patterned in one common process. This simplifies the manufacturing. It further avoids the necessity of alignment.
- The ports indicate locations where the optical signal beams enter the optical cross-connect switch and not a special embodiment of the entry points or the means by which the optical signal beams enter the optical cross-connect switch. A port may therefore be a unit in which optical waveguides are coupled or a location where optical signal beams are entering the optical cross-connect switch e.g. by means of a waveguide which is coupled to an external device. In this case the location of the port could be defined as the output port of the external device.
- The steering device can be arranged in a cavity in the substrate. The optical cross-connect switch then comprises a substrate, which is partially covered by a waveguide layer and a cladding layer, patterned for example by etching processes, with at least one waveguide, connected with one end to one of the optical ports and with the other end, comprising core and cladding, unsupported by the substrate or remaining layers and extending into a switching plane above the cavity, which is located in the substrate. In the cavity the steering device is arranged, designed to direct the free waveguide end in a selectable direction within the switching plane towards an optical element, such as a free end of a further waveguide, designed to receive or send optical signal beams.
- The optical cross-connect switch can be used to construct large switching fabrics with numerous peripheral optical ports or small switching units within an optoelectronic comprising for example only three or two internal optical ports that are connected for example to communication modules of the optoelectronic integrated circuit.
- The optical cross-connect switch preferably comprises a slab waveguide module positioned within the switching plane in order to transfer the optical signal beams between a waveguide connected to the first set of optical ports and a waveguide of the second set of optical ports. The slab waveguide module provides for a guiding of the optical signal beam that is laterally less constraint than vertically.
- The steering device preferably comprises a head element, which is pivotally supported by an anchor and which holds a corresponding free waveguide end in such a way that the head element can be rotated by means of an actuator thus directing the free waveguide end in a selectable direction within the switching plane.
- The head element is preferably connected to the actuator and to the anchor by means of elastic beams which support rotation of the head element around an axis that is aligned substantially perpendicular to the switching plane thus keeping the free waveguide end in every direction angle stabilized within the switching plane.
- In a further embodiment the head element is connected to the actuator by means of the free waveguide end which is elastically suspended on the front end of the actuator. This embodiment allows the fabrication of the head element and the actuator independently from each other.
- The actuator is designed to rotate the head element with forces generated by means of a piezoelectric, electrostatic, acoustic or thermal effect.
- Preferably the actuator is a thermally controlled cantilever arranged approximately in parallel to a free waveguide end. The actuator has one or two arms, each comprising several actuating beams arranged substantially in parallel, connected to each other at their ends and arranged adjacent to heater elements for individually heating and thus asymmetrically expanding the actuating beams in order to generate a lateral movement at the front end of the actuator and consequently a rotation of the connected head element relative to the supporting anchor.
- The solution allows to fabricate the elements of the steering device including the interconnecting beams in one piece respectively from the same substrate by use of micromachining technology. Cross-connect switches can therefore be fabricated at reduced cost with high packing density.
- Some of the objects and advantages of the present invention have been stated, others will appear when the following description is considered together with the accompanying drawings, in which:
- FIG. 1 shows a sectional view of an optical cross-connect switch with a first and a second set of waveguides arranged with their free waveguide ends aligned by means of waveguide steering devices on opposite sides of a slab waveguide module;
- FIG. 2a shows a more detailed view of two of the waveguide steering devices of the optical cross-connect switch shown in FIG. 1;
- FIG. 2b shows a side elevation of a cut along line A-A in FIG. 2a;
- FIG. 3 shows a more detailed view of a head element of a waveguide steering device;
- FIG. 4a shows a three-dimensional view of a part of an optical cross-connect switch embedded in a layered optoelectronic integrated circuit with a free waveguide end pointing into a first direction;
- FIG. 4b shows a three-dimensional view of the part of an optical cross-connect switch embedded in a layered optoelectronic integrated circuit with the free waveguide end pointing into a second direction;
- FIG. 5 shows a second embodiment with two waveguide steering devices; and
- FIG. 6 shows a third embodiment with two waveguide steering devices.
- All the figures are for sake of clarity not shown in real dimensions, nor are the relations between the dimensions shown in a realistic scale.
- FIG. 1 shows a sectional view of an
optical cross-connect switch 1 comprising asubstrate 8 bearing aframe 82 and a first set ofwaveguides substrate 8 has a sheetlike form, i.e. is essentially planar, which means that it has a substrate plane whose extension in both plane dimensions is larger than the substrate thickness. Theswitch 1 further comprises a first set ofoptical ports first end 1 a of thesubstrate 8. Each of thewaveguides first waveguide end 21 to one of theoptical ports frame 82 comprises awaveguide layer 84 exhibiting a preferential mode-propagation direction in a plane parallel to or identical with the substrate plane. Theframe 82 further comprises on thewaveguide layer 84 on its side opposite thesubstrate 8, acladding layer 83. - The
frame 82 is here unified with the first waveguide ends 21. More precisely the first waveguide ends 21 and theframe 82 are of unitary construction. Hence the first waveguide ends 21 are also disposed on thesubstrate 8, which makes the first waveguide ends 21 to fixed waveguide ends 21. Thewaveguide layer 84 and thecladding layer 83 are patterned to form the fixed waveguide ends 21. In particular, thewaveguide layer 84 is patterned to comprise for each of the waveguides 201-206 a ridge that forms a respective waveguide core. In the manufacturing step for thecladding layer 83, thecladding layer 83 is automatically patterned by depositing it on the patternedwaveguide layer 84 thereby forming over each waveguide core ridge a cladding ridge with inclined sidewalls. This means that the fixed waveguide ends 21 here comprise a patterned part of thewaveguide layer 84 andcladding layer 83. - The opposite waveguide ends22 of the waveguides 201-206, extend partially across a
first cavity 81 a in thesubstrate 8. Since these opposite waveguide ends 22 are standing unsupported and free with respect to thesubstrate 8 they are also referred to as free waveguide ends 22. The free waveguide ends 22 and the fixed waveguide ends 21 are of unitary construction. This can be achieved by manufacturing them from a common source structure, preferably in a common process step. Here the source structure can be thewaveguide layer 84 with the waveguide core ridge and thecladding layer 83 with the cladding ridge. By removing the corresponding parts of thewaveguide layer 84 andcladding layer 83, namely the regions beneath the ridge, the remaining structure, comprising the waveguide core with the corresponding cladding, represent the waveguides 201-206 comprising the patternedwaveguide layer 84 andcladding layer 83, lying with their fixed waveguide ends 21 on thesubstrate 8. - A manufacturing process step sequence for manufacturing the above described structure would hence be to provide the
substrate 8, deposit thereon the patternedwaveguide layer 84, deposit thereon thecladding layer 83, remove these two layers in the area around the free waveguide ends 22 and above thefirst cavity 81, then creating thefirst cavity 81 by removing thesubstrate 8 in that area. - For each of the free waveguide ends22 of the first set of waveguides 201-206, in the
first cavity 81 asteering device 10 is arranged for directing the respectivefree waveguide end 22 in a selectable direction within a switching plane, that is preferably identical with or parallel to the plane of thesubstrate 8. - On the end opposite the
first end 1 a, referred to asopposite end 1 b of thesubstrate 8, is disposed a second set ofwaveguides optical ports waveguides first waveguide end 21 to one of theoptical ports second cavity 81 b above thesubstrate 8 within theframe 82. For each of the free waveguide ends 22 of the second set of waveguides 211-216, in thesecond cavity 81 b asteering device 10 is disposed for directing the respectivefree waveguide end 22 in a selectable direction within the switching plane. The arrangement of theswitch 1 is here symmetric along the line separating the oneend 1 a and theopposite end 1 b of theswitch 1. - By changing the direction of the
free waveguide end 22 of one waveguide of the first set of waveguides 211-216, anoptical signal beam 4 guided in that waveguide can be directed towards an optical element designed to receive thatoptical signal beam 4, such as here thefree end 22 of one waveguide of the second set of waveguides 211-216 at theopposite end 1 b of the opticalcross-connect switch 1. - The
steering device 10 comprises anactuator 5 and ahead element 6. The end of thefree waveguide end 22 that is remote from thesubstrate 8 and extending partially across thefirst cavity 81 a is hereinafter referred to as remote waveguide end. Theactuator 5 is here a longitudinal element that is disposed along some part of the length of thefree waveguide end 22 and is designed to be able to provide for a lateral force on thefree waveguide end 22 with respect to the fixedwaveguide end 21. More precisely theactuator 5 extends from thesubstrate 8 into thefirst cavity 81 a along some part of the length of thefree waveguide end 22. - The
head element 6 is arranged at the remote waveguide end and is rotatable for changing the direction of the correspondingfree waveguide end 22, i.e. the direction of theoptical signal beam 4 emanating from the remote waveguide end. Thefree waveguide end 22, respectively the remote waveguide end thereof, is preferably preshaped such that it is compliant to flexure and/or torque applied by thesteering device 10, and prevented from retraction in case that the direction is changed. Such a shape would for example be an S-shape. - For changing the beam direction at the
free waveguide end 22, theactuator 5 provides for a lateral force and hence a lateral shift of the remote waveguide end of thefree waveguide end 22. That lateral shift is translated by means of thehead element 6 into a swiveling of the remote waveguide end, which has the effect of a corresponding swiveling of the beam direction. - The optical
cross-connect switch 1 further comprises aslab waveguide module 3 that is arranged between thefirst cavity 81 a and thesecond cavity 81 b. Theslab waveguide module 3 is designed to guide the one or moreoptical signal beams 4 between the free waveguide ends 22 of the waveguides of the first set of waveguides 201-206 and the waveguides of the second set of waveguides 211-216. Between theslab waveguide module 3 and each of the free waveguide ends 22 agap 32 exists. Theslab waveguide module 3 preferably also comprises a part of thewaveguide layer 84 and thecladding layer 83 on thesubstrate 8, and can therefore easily be fabricated by removing a corresponding section from thewaveguide layer 84 and thecladding layer 83. This then means that theslab waveguide module 3 and the waveguides 201-206 are of uniform construction. Automatically, by having been formed from thesame waveguide layer 84 andcladding layer 83, theslab waveguide module 3 and the waveguides 201-206 lie in a common plane which plane is identical or parallel to the switching plane. In this case the waveguides 201-206 and theslab waveguide module 3 are fabricatable in a single patterning process. Such patterning process can be e.g. a lithographic process, involving photoresist-deposition, masking, illumination, and etching. The manufacturing sequence described above automatically creates theslab waveguide module 3 by leaving thesubstrate 8 with thewaveguide layer 84 and thecladding layer 83 in the area outside of thecavities - The
steering device 10 is located between thewaveguide layer 84 and thesubstrate 8. This means that thecavities substrate 8 and that theslab waveguide module 3 not only comprises a patterned part of thewaveguide layer 84 andcladding layer 83, but also the corresponding patterned part of thesubstrate 8. - The structure and functionality of the optical
cross-connect switch 1 is preferably symmetric. In order to transfer theoptical signal beams 4 from the first set of waveguides 201-206 to the second set of waveguides 211-216, the corresponding opposite free waveguide ends 22 are aligned towards each other by means of thecorresponding steering devices 10, which here are identical in their design to thesteering devices 10 for the first set of waveguides 201-206. - One such
optical signal beam 4 can be transmitted between thefree waveguide end 22 of one waveguide of the first set of waveguides 201-206 and thefree waveguide end 22 of one waveguide of the second set of waveguides 211-216 through free-space and/or through theslab waveguide module 3. - In order to keep the coupling properties between the waveguides211-216 and the
slab waveguide module 3 substantially constant over the range of different directions of thefree waveguide end 22, theslab waveguide module 3 comprises adjacent to each remote waveguide end anadaptation section 31 which is curved in such a way that thegap 32 between theslab waveguide module 3 and the respectivefree waveguide end 22 is substantially constant for several selectable directions. - The optical
cross-connect switch 1 hence allows the selectable transfer of theoptical signal beams 4 between the free waveguide ends 22 of the first set of waveguides 201-206 and the free waveguide ends 22 of the second set of waveguides 211-216 through theslab waveguide module 3 that acts as a coupler element. - The directional steering of the
free waveguide end 22 can be performed with a micro-electromechanical-system, which here is thesteering device 10. Thesteering device 10 comprises thehead element 6 designed to hold and rotate the corresponding remote waveguide end relative to an axis aligned substantially perpendicular to the switching plane. A rotation of thehead element 6 in order to establish a selected signal beam path within the switching plane is performed by an electromechanical actuator, which here is theactuator 5. - The
frame 82 can serve for coupling the waveguides 201-206 to the optical ports 101-106 which can be optical fiber ends. Therefore theframe 82 can e.g. be structured to have grooves, e.g. V-grooves for receiving and aligning the optical ports 101-106. This function can also be achieved by other means. Hence theframe 82 is not essential for the functionality of theswitch 1. - FIG. 2a shows two of the
waveguide steering devices 10 of the opticalcross-connect switch 1 of FIG. 1. FIG. 2b shows a cut view along the line A-A in FIG. 2a. - One of the
steering devices 10, here referred to as thefirst steering device 10, holds thefree waveguide end 22 of afirst waveguide 201 and one of thesteering devices 10, here referred to as thesecond steering device 10, holds thefree waveguide end 22 of asecond waveguide 202. - Each of the
steering devices 10 comprises thehead element 6, which is pivotally supported by ananchor 61 and which holds thefree waveguide end 22 at its end remote from theframe 82. It further comprises theelongated actuator 5 having two ends, one fixed end and one free end. Theactuator 5 is thermally driven. It is arranged substantially parallel to the correspondingfree waveguide end 22 and is equipped with twoarms 51, each comprising two parallel actuation beams 52 in line withlever elements 53 that are connected to each other at their ends by means of ayoke 58 which holds ayoke beam 59. The actuation beams 52 which at the fixed end of theactuator 5 emanate from thesubstrate 8, carry electricallyresistive heaters actuator 5 and consequently a rotation of the connectedhead element 6 relative to theanchor 61. For effecting the asymmetrical expansion of the actuation beams 52, also only one of the actuation beams 52 can be equipped with theheater 54. - The lateral movement of the free end of the
actuator 5 hence causes a rotational movement of thehead element 6, turning the remote waveguide end of the attachedfree waveguide end 22 into a desired direction. The remote waveguide end of thefirst waveguide 201 is at least laterally fixed at thehead element 6 by means ofspacers 63, wherein “lateral” is meant in a direction within the switching plane, substantially perpendicular to the beam direction. - At each remote waveguide end, here a terminating
mode converter 23 is arranged, for collimating the outgoing beam of the respectiveoptical signal beam 4 in horizontal and/or vertical direction. The terminatingmode converter 23 has here a convex end surface that has substantially the same radius as the corresponding opposite surface of theslab waveguide module 3. Themode converter 23 is designed to create an expanded beam within thegap 32 between thefree waveguide end 22 and theslab waveguide module 3 thus optimizing the coupling efficiency therebetween but also preventing beam divergence in the slab waveguide region. Themode converter 23 which could comprise a gradually enlarged element of thefree waveguide end 22 acts as a collimating element focusing the emitted beam. Here, also thehead element 6 is shaped in a similar form at its end that is closer to theslab waveguide module 3. - A small lateral movement of the
actuator 5 results in a relatively large deflection of thefree waveguide end 22 being translated into a corresponding big angle change of the corresponding beam direction. Such asteering device 10 and hence the whole opticalcross-connect switch 1 can hence be realized in small dimensions, nevertheless allowing a relatively broad selection of possible beam directions. - The actuation of the
first steering device 10 holding thefirst waveguide 201 is depicted in FIG. 2a in an off-state. The actuation of the secondwaveguide steering device 10 holding thesecond waveguide 202 is in contrast depicted in an on-state, resulting in the guidance of the correspondingoptical beam 4 through the corresponding turned remote waveguide end at an angle Q towards a receiving waveguide, e.g. thewaveguide 214 as shown in FIG. 1. - The actuation of the
steering device 10 holding thesecond waveguide 202 is effected by heating and thereby thermally expanding thebeams 54 on one side of eacharm 51 more than thebeams 55 on the other side of eacharm 51. This results in a lateral movement of the front end of thearms 51 and of theyoke 58 and a corresponding turn of thehead element 6 and the remote waveguide end of the corresponding steeredwaveguide end 22. Heating and thermally expanding theother beams 55 more than the correspondingbeams 54 would result in a lateral movement of the front end of thearms 51 in the opposite direction. The thermally drivenactuators 5 can be used for creating large displacements of the yokes 85 and hence the remote waveguide ends with high forces. They can be based on the thermal expansion of two different materials (bimaterial actuators) or of two coupled beams of an actuator arm at different temperatures. The disadvantage of coupled linear and angular movement is overcome by coupling two of these arms. - The
actuator 5 is at its fixed end supported by thesubstrate 8. Theanchor 61 is realized as a protrusion on thesubstrate 8. Thefree waveguide end 22 hence runs along substantially the same direction as theactuator 5, above the same with respect to thesubstrate 8 and is held at its remote waveguide end by thehead element 6. - The process for manufacturing the
switch 1 including thesteering devices 10 would include a step of manufacturing thesteering device 10 by structuring thesubstrate 8 in thecavity steering device 10. In that case thesteering device 10 and thesubstrate 8 would be of uniform construction. This would not include theheaters heaters steering device 10 that comprises the substrate material. The structuring of thesubstrate 8 to form thesteering device 10 without theheaters steering device 10 separately and then assemble it into thecavity substrate 8. Also a combination of such assembly with parts of thesteering device 10 having been manufactured directly within thecavity substrate 8, e.g. theanchor 61, can be made. - FIG. 3 shows a more detailed view of the anchored
head element 6 of the secondwaveguide steering device 10 shown in FIG. 2a. - The
waveguide steering device 10 comprises thehead element 6 which by means of elasticprimary beams 64 andsecondary beams 65 is connected to theanchor 61. Theanchor 61, which may comprise one or more elements, acts as a pivot-bearing allowing thehead element 6 to rotate around the point where theprimary beams 64 are connected to theanchor 61. - The
steering device 10 further comprises theactuator 5 with a front end comprising theelastic yoke beam 59, which by means of the further beam orrod 62 is connected to thehead element 6. Theelastic yoke beam 59 is attached to theyoke 58 and provides for a fixation of thehead element 6 to theactuator 5 that keeps the remote waveguide end of thefree waveguide end 22 tiltable with respect to its longitudinal extension. - The elements of the
steering device 10 can be at least partially fabricated in one piece on thesubstrate 8 being a bulk substrate, by means of micro-fabrication. The opticalcross-connect switch 1 can therefore be realized for example in an optoelectronic integrated circuit without insertion of externally manufactured optical elements such as mirrors or lenses. - FIG. 4a shows a three-dimensional view of a section of an optoelectronic integrated circuit comprising the
switch 1 as described. From the patternedwaveguide layer 84 and the patternedcladding layer 83 on thesubstrate 8 extend the twowaveguides substrate 8 comprises thefirst cavity 81 a with thesteering device 10 integrated therein which holds thefree waveguide end 22 of thewaveguide 201 fastened to itshead element 6. Thehead element 6, which is rotatably mounted by means of the anchor 61 (not shown), is connected to theyoke beam 59 of the thermally drivenactuator 5 which extends out of a section of thesubstrate 8, which section forms a sidewall of thefirst cavity 81 a. On the twoactuating beams 52 of eachcantilever arm 51 the electricallyresistive elements actuator 5 and consequently a rotation of the connectedhead element 6 relative to theanchor 61. - In FIG. 4b the same arrangement as in FIG. 4a is depicted, but here the
free waveguide end 22 is deflected to change its output direction. The twoactuating beams 52 of eachcantilever arm 51 are asymmetrically expanded, thereby generating a lateral movement at the front end of theactuator 5 and consequently a rotation of the connectedhead element 6 relative to theanchor 61. A force F generated by theactuator 5 is applied to the pivotally supportedhead element 6, which transforms this force F into a corresponding rotational moment M to the remote waveguide end of thefree waveguide end 22 of thefirst waveguide 201. - The
gap 32 between thefree waveguide end 22 and theadjacent adaptation section 31 of theslab waveguide module 3 is shown expanded. - The
slab waveguide module 3 is an element that can be fabricated from thewaveguide layer 84, thecladding layer 83 and thesubstrate 8. Thisslab waveguide module 3 has the functionality of a planar waveguide layer, i.e. has extensions in a plane parallel to or identical with the substrate plane or the switching plane, which here is the plane in which the various selectable directions of theoptical signal beams 4 lie, which extensions are bigger than the thickness of theslab waveguide module 3. Theslab waveguide module 3 thereby allows a transfer of theoptical signal beam 4 that is laterally, i.e. in the switching plane, less constraint than in the planes perpendicular thereto. - However as mentioned before, the
free waveguide end 22 could also be aligned with a further optical receiver such as another waveguide end which might be firmly aligned. In such a case or in a case where only a discrete set of signal beam paths is desired, theslab waveguide module 3 could be patterned accordingly. The opticalcross-connect switch 1 could therefore be realized with thesteering device 10 holding thefree waveguide end 22 of thefirst waveguide 201 and e.g. two angularly offset fixed waveguide ends 22 located in opposition thereof. - FIG. 5 shows a second embodiment of the
waveguide steering device 10. Thewaveguide steering device 10 pertaining to thefirst waveguide 201 is depicted in an off-state and comprises theactuator 5 with asingle arm 51 which over anelastic beam 62 is connected to thehead element 6 which is further connected to theanchor 61 acting as pivot bearing. Thearm 51 comprises twoactuation beams 52 with oneheater anchor 61 is arranged sideways to thearm 51 when viewed perpendicular to the switching plane, i.e. in direction of the axis of theanchor 61. Thewaveguide steering device 10 pertaining to thesecond waveguide 202 is depicted in an on-state, i.e. by deflection of theactuator 5 thehead element 6 is turned around the fixing point provided by theanchor 61. - The
waveguide steering device 10 shown in FIG. 6 comprises thefirst waveguide 201 with the dual-arm cantilever actuator 5 and thehead element 6, which are connected to one another by means of the attachedwaveguide end 22 of the correspondingfirst waveguide 201. Eacharm 51 comprises the twoactuation beams 52 with oneheater head element 6 is connected via the primary andsecondary beams anchor 61 acting as pivot bearing. Theanchor 61 comprises here two anchor elements, one of them respectively being arranged to either side of the remote waveguide end and being fixed at thesubstrate 8 and being connected to each other via the primary andsecondary beams actuator arms 51 are connected to abearing element 56 by means of the yoke beams 59. The bearingelement 56 and thehead element 6 which are mechanically connected by means of thefree waveguide end 22 are mutually aligned and rotated correspondingly whenever a lateral movement of theactuator arms 51 occurs, thus directing thefree waveguide end 22 in a selected direction. Thewaveguide steering device 10 pertaining to thefirst waveguide 201 is depicted in an off-state. Thewaveguide steering device 10 pertaining to thesecond waveguide 202 is depicted in an on-state, i.e. by deflection of theactuator 5 thehead element 6 is turned around the fixing point provided by theanchor 61. - The solution can also be applied in cross-connect systems comprising protection fibers that are assigned to a single fiber for protection purposes only. A protection fiber could therefore be aligned firmly towards an
opposite waveguide end 22 which in case of a failure of the standard connection would be redirected towards theend 22 of the protection fiber. - A lower cladding layer can be arranged under the waveguide layer. Such lower cladding layer can e.g. comprise an oxide layer such as SiO2 on a
silicon substrate 8. This lower cladding layer then provides for a more symmetrical mode form, facilitating coupling to other waveguides. All patterning steps that affect thewaveguide layer 84 can be performed on thecladding layer 83 and the lower cladding layer as well, such that the final pattern is identical through all three layers. - The
complete steering device 10 can be manufactured from thesubstrate 8, using microfabrication, nanostructuring or lithographic process steps. For such process steps it is of advantage if the layout of thesteering device 10 is designed such that in a view perpendicular to the substrate plane, at least the arm orarms 51 are positioned lateral to thefree waveguide end 22. Thereby, thearms 51 can be manufactured by exposing thesubstrate 8 to processing means, such as optical, liquid or gaseous means, directed substantially perpendicularly to the substrate plane. The structure depicted in FIG. 4a is such a structure. All parts of thesteering device 10 that lie underneath thefree waveguide end 22 can be manufactured by applying process steps in which the processing agents can reach the structure to be manufactured also underneath thefree waveguide end 22. A possibility is also to apply process steps that reach the target location from underneath thesubstrate 8. Therefor openings that reach thecavity substrate 8, i.e. from the side opposite thecavity - What has been described is merely illustrative of the application of the principles of the present invention. Other arrangements can be implemented by those skilled in the art without departing from the spirit and scope of protection of the present invention.
- Any disclosed embodiment may be combined with one or several of the other embodiments shown and/or described. This is also possible for one or more features of the embodiments.
- It is obvious that a person skilled in the art can modify the shown arrangements in many ways without departing from the gist of the invention which is encompassed by the subsequent claims.
Claims (14)
1. An optical cross-connect switch comprising a waveguide connected with one waveguide end to a first optical port and connected with its other waveguide end to a steering device for directing an optical signal beam from said first optical port to a second optical port, said waveguide comprising a patterned waveguide layer partially disposed on a substrate.
2. The optical cross-connect switch according to claim 1 , further comprising a slab waveguide module designed to guide the optical signal beam and comprising a patterned waveguide layer disposed on the substrate.
3. The optical cross-connect switch according to claim 1 , wherein the waveguide layer is disposed adjacent a cladding layer.
4. The optical cross-connect switch according to claim 1 , wherein the steering device is located in a cavity in the substrate.
5. The optical cross-connect switch according to claim 1 , wherein the steering device and the substrate are substantially of unitary construction.
6. The optical cross-connect switch according to claim 1 , wherein the steering device comprises a rotatable head element at the other waveguide end for directing said optical signal beam in a selectable direction.
7. The optical cross-connect switch according to claim 6 , wherein the head element is rotatable by means of an actuator.
8. The optical cross-connect switch according to claim 7 , wherein the head element is connected to the actuator by means of one of an elastic beam and the other waveguide end.
9. The optical cross-connect switch according to claim 7 , wherein the other waveguide end is elastically connected to the actuator.
10. The optical cross-connect switch according to claim 7 , wherein the actuator is designed to provide a lateral shift of the other waveguide end.
11. The optical cross-connect switch according to claim 10 , wherein the head element is designed to translate the lateral shift into a rotation of the other waveguide end around a rotation axis.
12. The optical cross-connect switch according to claim 7 , wherein the actuator comprises several arms connected at one end to the substrate and connected at their other end to each other via a yoke that is connected to the head element via an elastic yoke beam.
13. The optical cross-connect switch according to claim 1 , wherein the other waveguide end is preshaped to comply with one of flexure and torque of the steering device.
14. The optical cross-connect switch according to claim 1 , wherein at the other waveguide end a mode converter is arranged for collimating the optical signal beam.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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EP01811267 | 2001-12-24 | ||
EP01811267.2 | 2001-12-24 |
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US20030123787A1 true US20030123787A1 (en) | 2003-07-03 |
US7082232B2 US7082232B2 (en) | 2006-07-25 |
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US10/318,615 Expired - Fee Related US7082232B2 (en) | 2001-12-24 | 2002-12-11 | Optical cross-connect switch |
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US20040022478A1 (en) * | 2002-08-05 | 2004-02-05 | Luminos Industries Ltd. | Moving fiber optical switch |
US20140212089A1 (en) * | 2013-01-28 | 2014-07-31 | Harris Corporation | Actuator systems for deflecting optical waveguides, and devices for processing optical signals comprising same |
US8875311B2 (en) * | 2011-08-11 | 2014-10-28 | International Business Machines Corporation | Scanning probe microscopy cantilever comprising an electromagnetic sensor |
US11221447B1 (en) * | 2016-12-23 | 2022-01-11 | Acacia Communications, Inc. | Suspended cantilever waveguide |
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GB0312443D0 (en) * | 2003-05-30 | 2003-07-09 | Newoptics Ltd | Optical multiplexer |
US7612329B2 (en) * | 2004-09-13 | 2009-11-03 | Space Photonics, Inc. | Apparatus and method for free space optical communications beam steering without gimbals |
US8160452B1 (en) | 2008-01-07 | 2012-04-17 | Space Photonics, Inc. | Rapid acquisition, pointing and tracking optical system for free space optical communications |
US10564358B2 (en) * | 2017-05-30 | 2020-02-18 | Valorbec Societe En Commandite | Micromechanically actuated deformable optical beam steering for wavelength tunable optical sources, filters and detectors |
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US6404944B1 (en) * | 2000-03-17 | 2002-06-11 | Unveristy Of Central Florida | Monolithic integrated active semiconductor optical switch for a 1×N interconnect switch |
US6549700B1 (en) * | 2001-06-05 | 2003-04-15 | Sandia Corporation | Optical switch using Risley prisms |
US6865310B2 (en) * | 2002-08-09 | 2005-03-08 | Fujitsu Limited | Multi-layer thin film optical waveguide switch |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
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US20040022478A1 (en) * | 2002-08-05 | 2004-02-05 | Luminos Industries Ltd. | Moving fiber optical switch |
US6990267B2 (en) * | 2002-08-05 | 2006-01-24 | Luminos Industries Ltd. | Moving fiber optical switch |
US8875311B2 (en) * | 2011-08-11 | 2014-10-28 | International Business Machines Corporation | Scanning probe microscopy cantilever comprising an electromagnetic sensor |
US20140212089A1 (en) * | 2013-01-28 | 2014-07-31 | Harris Corporation | Actuator systems for deflecting optical waveguides, and devices for processing optical signals comprising same |
US9513440B2 (en) * | 2013-01-28 | 2016-12-06 | Harris Corporation | Actuator systems for deflecting optical waveguides, and devices for processing optical signals comprising same |
US9523817B2 (en) | 2013-01-28 | 2016-12-20 | Harris Corporation | Actuator systems for deflecting optical waveguides, and devices for processing optical signals comprising same |
US11221447B1 (en) * | 2016-12-23 | 2022-01-11 | Acacia Communications, Inc. | Suspended cantilever waveguide |
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